The present invention relates generally to the field of grain processing and specifically to an apparatus and method for cutting xe2x80x9cgroatsxe2x80x9d (de-hulled oats), other grains, or other granular material. Finely cut groats commonly are used for the production of xe2x80x9cquick-oatsxe2x80x9d and other oat-based food products. Because finely cut groats have a greater surface area to volume ratio than more coarsely cut groats, more surface area is available for a given volume of groats. This increased surface area allows greater contact between, for example, boiling water and the groats. As a result, the moistening and cooking of finely cut groats may be performed in a relatively short time, hence the name xe2x80x9cquick-oatsxe2x80x9d. The production of quick-oats, in addition to other types of oat-based food products, therefore depends upon the production of finely cut groats.
The basic technology for cutting granular material applies to a variety of grains for a variety of products. Each grain product and each different producer of grain products may require grain to be cut to a different degree of fineness. The present invention relates specifically to improvements that may increase grain cutting efficiency for grain cutting in general, for different grains and for different levels of desired fineness. Therefore, although the examples detail the fine-cutting of groats, it will be apparent to one skilled in the art that the present invention may be applied to different materials and to make coarser, or finer, end products.
The prior art technology for cutting groats includes the use of a drum that spins on a horizontal axis and contains a plurality of perforations in its sidewall. The perforations in the spinning drum""s sidewall allow groats to extend from the drum interior at least partially through the sidewalls where they may contact one or a series of stationary cutting blades that are arranged in close proximity to the drum sidewall exterior. U.S. Pat. No. 307,882 (the ""882 patent) discloses a typical prior art groat cutting apparatus that employs this technology. The common xe2x80x9cKip Kellyxe2x80x9d type cutter (developed many years ago and currently marketed by Arrow Corp. of Winnipeg Canada) also employs this basic technology. Other examples of prior art groat cutting devices include U.S. Pat. Nos. 208,970 (the ""970 patent), 241,249 (the ""249 patent), and 279,594 (the ""594 patent).
As disclosed in the ""882 patent, the rotary groat cutting apparatus receives groats into the interior of the perforated, spinning drum. The spinning drum is nested in a blade assembly that consists of a series of four knife blades separated by grain support surfaces. Groats of grain extend through the perforations and contact either a blade or a support surface between the blades. The spinning drum causes the groats to ride upon the support surfaces until the groats encounter a cutting blade. When a groat is cut sufficiently fine, its cut portions exit the drum completely, and another groat extends through the perforation. The apparatus disclosed in the ""882 patent, therefore, utilizes only a fraction of the blade assembly for actual cutting.
The ""882 patent also discloses a separate, spinning cylinder or xe2x80x9cpinwheelxe2x80x9d located on the exterior of the spinning drum. The pinwheel contains pins aligned with passing perforations in the drum. These pins clear the perforations of groat portions or other obstructions. In the ""882 patent, separate gear mechanisms on the drum and pinwheel work cooperatively to rotate the drum and pinwheel. Alternatively, the pinwheel may serve as the source of rotation for the drum. Because the spinning drum and pinwheel spin cooperatively, it is important to maintain precise alignment of the pins with the drum perforations to avoid damage to the drum or pins and to avoid the loss of metal from the drum or pins into the groat stream.
A primary cause of the loss of alignment between the pinwheel pins and the drum perforations is contamination of the pinwheel assembly with dust from the groat cutting process (which inherently produces a great deal of dust). Over time, this dust tends to work its way into spaces between machine components. The ""882 patent discloses a solid pinwheel assembly that consists of one cylinder having a plurality of pins that extend from its perimeter. This solid cylinder design is only minimally susceptible to dust because it has few seams into which dust may migrate. Unfortunately, this solid cylinder design demands repair or replacement of the entire pinwheel cylinder when only one or a few pins are damaged. Therefore, a more typical pinwheel design consists of a series of parallel rings. Parallel ring construction allows removal and replacement of a damaged ring (only a portion of the pinwheel) when only one or a few pins become damaged. Unfortunately, this advantageous design itself leads to pin misalignment as seams are inherent in the parallel ring construction, and migrating dust may force the parallel rings apart. There is, therefore, a need for a pinwheel assembly improvement to prevent the migration of dust into the pinwheel assembly while maintaining the advantage of a parallel ring construction.
The knife blades mounted generally below and near the exterior of the spinning drum also require periodic replacement or maintenance and they are typically mounted individually upon a knife mounting assembly. As discussed, the ""882 patent discloses the use of four independent knife blades separated by a casing upon which protruding groat portions may xe2x80x9cridexe2x80x9d as the drum spins. The ""249 patent discloses the use of a plurality of knife blades wherein the blades are xe2x80x9csubstantially tangentialxe2x80x9d to the spinning drum. Similarly, the common xe2x80x9cKip Kelly Cutterxe2x80x9d utilizes a series of knife blades that form a xe2x80x9cnestxe2x80x9d generally around the bottom half, or a portion of the bottom half of the spinning drum. Over time, these knife blades may loosen or slip and cause damage to the rapidly spinning drum and blades.
The knife blades and pinwheel assemblies, of course, must be replaced periodically. However, when blades slip or pins become misaligned, contact with the rapidly spinning drum needlessly cuts short the xe2x80x9clifexe2x80x9d of these components. In addition, damage to the drums demands repair or replacement of the drums, which are themselves expensive, precision-engineered components. The replacement of drums, pinwheels, or blades necessarily demands lost production associated with each stopped machine and labor expenses associated with the replacement of parts. There is, therefore, a need for a means to prevent or minimize instances of contact between the blades and the spinning drum as well as a means to prevent the misalignment of pins and drum perforations.
In prior art groat cutting devices, even when a series of knife blades were employed, most cutting was performed by only a limited number of blades located at an effective cutting region generally at the bottom or extreme bottom of the knife blade assembly. This effective cutting region varied depending on the type of grain being cut and the desired level of fineness or coarseness. The focus of cutting in an effective region occurs because gravity is the primary force that draws groats to the perimeter of the rotating drum, augmented only in small part by centrifugal force. Therefore, gravity makes groats available for cutting along a majority of the bottom of the spinning drum during operation. It is only in the effective cutting region at the bottom of the profile where the pull of gravity acts to move the grains directly into the perforations. At side regions, the pull of gravity aids to a lesser extent and groats are less effectively cut. Therefore, there is a need for an improved rotary granulator that more effectively utilizes knife blades mounted beyond the limited effective cutting region currently found at the bottom or extreme bottom of the spinning drums.
Finally, groat cutting efficiency is decreased by groats that enter the interior of the spinning drum but fail to disburse evenly throughout the drum so as to protrude through the perforated sidewall at all locations along longitudinal expanse of the sidewall. In general, for a given flow rate of groats, there is a drum retention time that represents the average time spent in the interior of the spinning drum for a groat. This retention time is roughly proportionate to the volume of the spinning drum occupied by grains during operation, divided by the volumetric flow rate of groats through the machine. The groat flow rate may be maximized, and the groat retention time may be minimized, by minimizing the number of xe2x80x9cemptyxe2x80x9d perforations that pass knife blades during each rotation of the drum. There is therefore a need for an improved rotary granulator that minimizes drum retention time and maximizes groat flow rate by more effectively utilizing all available sidewall perforations through each rotation of the drum.
The present invention is an improved grain cutting apparatus comprised of a perforated drum that spins on a horizontal axis. A pinwheel assembly spins cooperatively with the perforated drum, and pins on the pinwheel assembly engage and disengage drum perforations as the drum and assembly spin. Groats are received into the interior of the perforated drum and a grooved baffle in the interior of the perforated drum directs groats towards passing perforations in the drum sidewall. These groats eventually reach the sidewall and extend partially through the perforations. The grooved baffle prevents the incoming groat stream from remaining in a focused stream, and instead diffuses the stream to direct groats towards perforations along the entire length of the sidewall.
The protruding groats contact one or a series of stationary knife blades. The knife blades are mounted so that the cutting edge of each blade forms an identifiable angle of contact with a line tangent to the drum sidewall at the location of the blade. Different angles of contact are employed for blades at different locations on the blade assembly. This varied knife blade profile extends the effective cutting region beyond the traditional bottom region of the assembly to include blades along the rising sides of the assembly. This variation in the angles within the blade assembly allows cutting to occur over a greater region of the blade assembly and dramatically enhances groat cutting throughput and efficiency.
The present invention also incorporates improved knife blade supports with toe stops to further secure the knife blades and prevent the blades from slipping and contacting the spinning drum.